About my neighbour's building without planning permission?

[CaptainWizzle]

So my partner and myself finally bought our first house just over a year ago. We're slowly doing it up and have loved living here! We have a great relationship with our neighbours either side but haven't had any real contact with the people who live on the street behind us.

This week the people who live in the house behind us (we share a boundary at the end of both our gardens) started building a structure in the back of their garden, only about 30cm (or maybe less) away from the fence we share. I felt slightly disappointed that they hadn't let us know, but I don't have any objections to them trying to improve their garden.

As the week went on it became clear that this wasn't a small garden shed or summerhouse but a huge outhouse or workshop with concrete base right up against the boundary of our garden. With the apex roof overhanging the walls, I'd guess the lip of the roof is probably only about 10cm away from the boundary. The total height of the structure looks to be about 11-12ft tall.

I've checked out the building regulations in my area, and a structure of this size, this close to the boundary definitely requires planning permission.

I've tried to talk to the builders putting it up but they didn't really want to discuss it with me, to the point of seemingly ceasing work whenever I go into the garden.
I've tried to contact the owners, and have called round the house to discuss it. They didn't answer the door despite definitely being in.

The only real options for me are to let the structure go up, or to report them to the local council, ensuring a toxic relationship with them for as long as we live here. The structure itself isn't hugely offensive, but does dominate the view from our garden, as well making our already small garden feel very closed in. We also have no idea what the building will be used for, something that would have become apparent if planning permission had been obtained.

Other neighbours have expressed their concerns to me, and one in particular is largely impacted by it's location, but it does feel like as it's right up against my boundary it's my responsibility to make the complaint.

Am I overreacting or does this seem like a legitimate concern?

I agree, it needs reporting. Some people are cheeky fuckers and think that because it's their house or their land they can build what they like.

How do you know they haven't got planning permission?
The council will write to random neighbours . All planning permission will be on council website.
You do not need to be consulted regarding building .

Buckle up and be patient. If indeed the structure lacks planning permission and should have had it, the first port of call from the council’s point of view (assuming you grass then up) would be to require a retrospective application. So get clued up on which policies from the statutory Local Plan, and any adopted design guidance, would be used to decide that application. Use those policies to prepare a well founded objection as opposed to ‘I don’t like it’. If the structure departs from said policies then the council should refuse unless there is special reason. But then, your neighbours have the right to appeal. So although the council have the ultimate ability to require demolition, this is at least a year and potentially more away.

username7000 RTFT. OP checked the planning website AND phoned the council.